Oklahoma City Police just dropped dramatic body cam footage … showing the intense moment cops shot an armed man in a fatal incident that began as a mental health call.

The clip’s a tough watch — It shows Brandon Lena, in distress, walking around with a pistol outside his house near Tinker Air Force Base.

Despite officers’ efforts to calm things down, it escalates quickly, ending with Lena’s death in the street.

Watch the video … Officers James Doran, Joshua Geerdes and Jimmy Hatfield introduce themselves as Crisis Intervention Team members … and they beg Lena to drop the gun. He’s repeatedly warned — but Lena points his gun straight at them.

Officers are then heard firing multiple rounds of gunshots at Lena … instantly killing him.